To write the ratio 42 to 49 as a fraction in lowest terms, we divide the numerator and denominator by the greatest common factor (GCD) of 42 and 49. The GCD of 42 and 49 is 7, so we can simplify the ratio as follows:
42 to 49 = 42 / 49 = (42 / 7) / (49 / 7) = 6 / 7
Therefore, the fraction 42/49 in lowest terms is 6/7.